Siena is a persitence library for Java inspired on the Google App Engine datastore.

Siena is a single API with many implementations. You can use siena with relational databases, with the Google App Engine's datastore or with Amazon's SimpleDB. There is also an implementation called siena-remote very useful if you want to use the Google App Engine's datastore remotely. Other implmenetations are planned such as: HBase, DBSLayer,...

Please check The siena-project website

Using siena-jdbc and Play! ? You can integrate Siena into Play! easily.